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Do I need double the usual RAM if I have 2 GPU's?

mwasielewski1990mwasielewski1990 Posts: 343
in Technical Help (nuts n bolts)

Sup everybody!

Like in the thread title. Currently I'm running on 1080ti with 32gb RAM. In a ~10GB vram scene, DAZ consumes about 23GB RAM. Do I need another 32GB if I shove another GPU in my system, or will the 2 GPU's share the data loaded into RAM upon render?

Comments

  • Johnathanbriscoe98Johnathanbriscoe98 Posts: 1

    As long as the second GPU is also 11gb vram you'll be great :) 

    From my experience, when I upgraded to 64 gigs of ram, the pc would start using more ram than before with no gain in performance, it was just like it knew it had more breathing room. But when I went to 32 again, it also stayed the same. Keep in mind I'm also running 2 2080 Ti's so it does fit your scenario as well :) I say you're fine until you start running a bunch of other programs like photoshop and what not at the same time.

  • mwasielewski1990mwasielewski1990 Posts: 343
    Johnathanbriscoe98 said:

    As long as the second GPU is also 11gb vram you'll be great :) 

    From my experience, when I upgraded to 64 gigs of ram, the pc would start using more ram than before with no gain in performance, it was just like it knew it had more breathing room. But when I went to 32 again, it also stayed the same. Keep in mind I'm also running 2 2080 Ti's so it does fit your scenario as well :) I say you're fine until you start running a bunch of other programs like photoshop and what not at the same time.

    Thanks for replying so fast :) But, when you had the 64g of ram, and you launched a big render, did DAZ take more RAM than usual (more ram than in case of a single GPU)?

    What motherboard do you have? I currently have a cheap mini-itx board so I'm looking for opinions on full atx boards as well (for i7 8700).

    Would MSI Z-390 A PRO be any good?

  • StrangeFateStrangeFate Posts: 803

    I wouldn't worry much about RAM with Iray. Daz may use more RAM and less Swap file if you have more RAM. I wouldn't put much stock into RAM numbers when running DAZ or Iray.

    The only thing that really matters for Iray is that the whole scene fits in your VRAM, otherwise it will drop to using the CPU instead of GPU.

    If you're using 2 GPUs, they will NOT share VRAM, the whole scene will be loaded into each GPUs VRAM. If 1 GPU has less VRAM than the other and the scene doesn't fit in it, it will drop that GPU and use only the one where the whole scene fits.

  • Dim ReaperDim Reaper Posts: 687

    You should be fine with 32GB.  I'm running a 2080ti and a 1080ti - both have 11GB, with 32GB RAM.  I find that on scenes where I'm hitting very close to the 32GB limit, it is likely that iray will drop to CPU anyway, so I end up optimising the scene, and it does nto go near 32GB. 

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